The vibration type angular velocity sensor utilizes the generation of vibration (hereinafter called as the Coriolis vibration) by causing the vibrator within the angular velocity sensor to make resonant drive (hereinafter called as the drive vibration) and applying an angular velocity in a rotation axis direction perpendicular to the drive axis direction of the vibrator, to apply a Coriolis force in a detection axis direction perpendicular to the rotation axis direction and the drive axis direction, and the applied angular velocity is obtained by signal processing the amplitude of the generated Coriolis vibration.
Therefore, the vibrator is provided with a driving electrode for drive vibration of the vibrator and a detection electrode for detection of the Coriolis vibration. For the detection electrode, there is a detecting type such as an electrostatic capacitance type that detects an amplitude according to an electrostatic capacitance change or a piezoelectric type that detects an amplitude by using the piezoelectric effect.
But, it is known that a micro vibration is generated in a detection axis direction even when the angular velocity is not applied actually. It is a vibration (hereinafter called as the self-vibration) in the detection axis direction generated as a result that the drive vibration applied in the drive axis direction of the vibrator has leaked in the detection axis direction due to a minute error or the like of a sensor element structure including the vibrator and its support portion, and this self-vibration generates in the same phase as the drive vibration. And, the self-vibration has a steady amplitude unless structural abnormality is not generated in the sensor element and a signal processing circuit configuring the angular velocity sensor.
Patent Literature 1 (JP-A 2000-171257) describes a vibration type angular velocity sensor which performs failure diagnosis using the self-vibration, and it is an example to perform self-diagnosis by monitoring the amplitude of the self-vibration by the angular velocity sensor which detects an angular velocity by extracting an amplitude of the Coriolis vibration from an electric signal outputted from the vibrator and including the Coriolis vibration and the self-vibration according to the angular velocity.